Shaped regenerated cellulose products having bacteriostatic properties



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on statesman 3,296,000 Patented Jan. 3, 1967 3 296 000 SHAPEDREGENERATED ClElLLULOSE PRODUCTS HAVING BACTERKOSTATIC PRQPERTIESGregory C. Bockno, Media, and Joseph W. Schapael, Morton, Pa, assignors,by mesne assignments, to FMC Corporation, San Jose, Calif., acorporation of Delaware No Drawing. Continuation of application Ser. No.261,195, Feb. 26, 1963. This application Apr. 6, 1966, Ser. No. 540,514

8 Claims.

This application is a continuation of our application Serial Number261,195, filed February 26, 1963, now abandoned.

The present invention relates to the production of shaped bodies, suchas filaments and fibers, of regenerated cellulose having bacteriostaticproperties.

Conventional procedures for imparting bacteriostatic properties toshaped bodies of regenerated cellulose generally involve impregnating orcoating of regenerated cellulose filaments, fibers or fabrics formedtherefrom with a suitable bacteriostatic composition followed by drying.Such bacteriostatic finishes often alter the hand or other physicalproperties of the treated materials and, more important, are generallyfugitive and are thus readily removed by laundering or leaching inwater.

It is an object of this invention to provide viscose solutions which arecapable of being coagulated to form improve-d shaped bodies ofregenerated cellulose having bacteriostatic properties.

It is a further object of this invention to provide im provedbacteriostatic regenerated cellulose filaments, fibers, fabrics and likestructures which retain their bac; teriostatic properties after aconsiderable number of launderings in an aqueous medium.

Still further objects and advantages of the present invention willappear in the following detailed description and claims.

In accordance with the present invention, regenerated cellulosefilaments, fibers and other shaped products having bacteria inhibitingproperties are formed from a viscose containing3,4,4-trichlorocarbanilide in the particulate form. Aside from theincorporation of the bacteriost atic compound noted, the viscose and thespinning bath employed in making the shaped regenerated celluloseproducts of the present invention may be of conventional or knowncomposition.

The manufacture of shaped products from viscose which exhibitbacteriostatic properties entails difiiculties which are not generallyencountered in melt or solution spinning procedures. The bacteriostaticcompound, and solvents used with such compound, must not only becompatible with the viscose solution, but must be capable of resistingthe acid environment and the subsequent processing procedures which arenormally involved in the manufacture of regenerated cellulose products.Experience has shown that many bacteriostatic compounds survive theviscose and spinning operations, only to be lost in the final processingprocedures which include de-s-ulfiding, bleaching and long periods ofwater washing. The present invention is predicated on our discovery that3,4,4'-trichlorocarbanilide can survice the viscose, spinning, andafter-treating procedures employed in making of regenerated celluloseproducts and methods which we have developed for incorporating the3,4,4-trichloroc-arbanilide compound into the viscose in precipitate orparticulate form.

The 3,4,4'-trichlorocarbanilide compound has very low solubility inwater. This characteristic is, of course, ideal since the activebacteriostatic agent which is removed from the surface of the shapedproducts through laundering is continuously replaced with additionalmaterial which is It is, however, soluble in certain organic solventsand thus various different procedures may be employed for introducingthe same into the viscose. In one such procedure, organic solventsolutions of 3,4,4- trichlorocarbanilide may be injected directly into aviscose under highshear blending conditions. Organic solvents found tobe satisfactory include polyethylene glycol, dimethyl formamide andacetone. Solutions of from about 1% to 10 or 15% or more of the3,4,4'-trichlorocar-banilide in the above-noted solvents provide for afine dispersion of the bacteriost-atic compound when injected into theviscose to the extent of from 0.3% to 7%, based on the weight of thecellulose. When relatively dilute solutions are employed, thebacte-riostatic compound appears as minute particles in the viscose andthus satisfactory spinning conditions can be well maintained. As theconcentration of the 3,4,4'-trichlorocarbanilide in the solvent isincreased, there is a greater tendency for the bacteriostatic compoundto precipitate as comparatively large plate-like crystals which readilyclog the spinneret openings.

In lieu of direct injection into the viscose, the organic solventsolution of the bacteriostatic compound, prepared as described above,may be precipitated as a sub-micron dispersed 3,4,4-trichlorocarbanilidein water containing a suitable surface active wetting or dispersingagent. For example, a 1.5% solution of 3,4,4'-trichlorocarbanilide inacetone or dirnethyl formamide, at room temperature, may be slowly addedto and vigorously mixed with an aqueous solution containing about 0.05%Du-ponol ME (sodium lauryl sulfate). The resulting dispersion containsabout 0.4% of 3,4,4'-trichlorocarbanilide having particle sizes of about1 micron or less, and may be injected directly into the viscose which isbeing spun. Alternatively, the dispersion may be centrifuged orpermitted to settle and decanted when concentration of thebacteriostatic compound and/or solvent recovery are importantconsiderations. With these last mentioned procedures, the bacteriostaticparticles are redispersed in an aqueous medium before injection into aviscose.

With the above-described precipitation procedure the small particles ofthe bacteriostatic particles provided are conducive to good spinningoperations for extended periods, and the bacteriostatic properties ofthe shaped regenerated cellulose products produced by this procedure aregenerally satisfactory. It has been found, however, that particles of3,4,4-trichlorocarbanilide of one micron or less are usually solvated toa large extent after some ten or fifteen laundering cycles. Thisparticular procedure is therefore best suited for producing shapedregenerated cellulose products which undergo little laundering or areintended to exhibit bacteriostatic properties for limited periods.

The 3,4,4-trichlorocarbanilide available commercially includes particleshaving an average size of from about 3 to 5 microns and a maximum sizewhich may range up to about 20 microns. By attriting this commercialcompound, as by a conventional dry-fluid energy grinding systom, theparticles can be reduced in size to an average of about 2 microns and amaximum of about 7 microns. Particles of this size are not entirelysatisfactory for good spinnability. These larger particles can beremoved by permitting the same to settle from an aqueous dispersion ofsuch attrited materials. For example, an aqueous dispersion originallycontaining about 8% of attrited 3,4,4- trichlorocarbanilide and asurface active agent, showed fewer particles larger than 3 or 4 micronsafter a settling period of between 3 and 4 hours. This remainingdispersion of classified particles may be injected into the viscose andenables acceptable spinning operations to be effected for extendedperiods.

leached under controlled latesjmrn within such plQdugls As noted above,the presence of large size particles It 2 Ni] renders the commerciallyavailable 3,4,4'-trichlorocarbanilide unsuitable for uninterruptedspinning operations. It was discovered, however, that these larger sizeparticles were caused by flocculation and agglomeration of the smallersize particles, and that this effect could be eliminated or materiallyreduced by employing a non-ionic (low foaming) surface active agent,such as Sterox AP (polyoxyethylene ether). For example, an 8.0%concentration of commercially available 3,4,4-trichlorocarbanilide maybe dispersed in an aqueous solution of 0.05% Sterox AP and may beinjected into a conventional viscose to provide the same with a 2%concentration of 3,4,4-trichlorocarbanilide, based on the weight of thecellulose. Such dispersion has been found to provide trouble-freespinning of regenerated cellulose filaments for extended periods with noaccumulation of insoluble matter being apparent on the filters orspinneret normally employed. As with the previously described procedure,this method of dispersing the 3,4,4-trichlorocarbanilide permitsparticles of the bacteriostatic compound larger than 1 micron, andpreferably particles having an average size of from 3 to 5 microns, tobe injected into the viscose so that resulting shaped regeneratedcellulose articles possess more permanent or lasting bacteriostaticactivity. This last described method also permits easier and moreeconomical preparation of the dispersion of the bacteriostatic compoundand is therefore the preferred method of the present invention.

The active bacteriostatic properties of the regenerated cellulose shapedproducts which are formed and the ability of the shaped products toretain such properties will, in general, vary with the amount andparticles size of 3,4,4-trichlorocarbanilide initially added to theviscose. As heretofore mentioned, particles of the bacteriostaticcompound having a size of 1 micron or less are readily solvated andshould therefore be employed in shaped products which are intended toundergo little or no laun dering. To provide shaped regeneratedcellulose products with durable or permanent bacteriostatic properties,that is, bacteriostatic activity which can withstand the usual textilefinishing operations and through at least twenty home-type or commerciallaundering cycles, the shaped products should include from about 1.0% to3.0% of 3,4,4-trichlorocarbanilide, based upon the weight of thecellulose. With the addition of as little as 0.125% of the3,4,4-trichlorocarbanilide, based upon the weight of the cellulose,shaped regenerated cellulose products are produced which exhibit somebacteriostatic activity. However, with such a small concentration of3,4,4-trichlorocarbanilide, the bacteriostati activity is rapidly lostduring normal use of the shaped products and rarely withstands as manyas ten home laundering cycles. When considering the bacteriostaticproperties from the standpoint of cost and/ or the useful life of theresulting regenerated cellulose products, the amount of3,4,4-trichlorocarbanilide employed should perhaps not exceed more thanto again based upon the weight of the cellulose.

The 3,4,4'-trichlorocarbanilide originally added to the viscose appearsas finely divided particles embedded in the finished regeneratedcellulose products, and do not materially affect. the hand, color,luster, dyeability nor launderability of such products.

As heretofore mentioned the viscose may be of conventional composition,containing from about 4% toabout 10% cellulose, about 4% to about 8%caustic soda and from about 30% to about 50% carbon disulfide; basedupon the weight of the cellulose. The modified viscose, that is, theviscose containing the 3,4,4'-trichlorocarbanilide may have any desiredsalt test at the time of spinning or extrusion. If desired, the viscosemay contain other known additives so as to improve the physicalproperties of the regenerated cellulose products and to alter the finestructure of the cellulose as is commonly practiced in the industry.

The viscose is formed in the conventional manner and either during itspreparation or just prior to spinning may be further modified by theaddition of a viscose or coagulation modifier. A large number ofmodifiers are known and are in use in the production of the varioustypes of viscose rayon. These modifiers include polyoxyalkylene glycolssuch as polyoxyethylene glycols, polyoxypropylene glycols and blockcopolymers of propylene and ethylene oxides; various amines includingmonoamines, diamines and polyamines such as diethylamine, dimethylamine,ethylene diamine and diethylene triamine; reaction products of alkyleneoxides with fatty acids, fatty alcohols, fatty amines, aromatic acids,aromatic alcohols, aromatic amines, partial esters of fatty acids andpolyhydric alcohols such as reaction products of ethylene oxide withlauryl alcohol, phenol, lauryl amine, glycerol monostearate, etc.;quaternary ammonium compounds and the like. The amount of modifier mayvary from about 2% to about 5%, based on the weight of the cellulose.

When using conventional viscose modifiers or coagulation modifiers, itis preferred to utilize a combination of modifiers such as a monoamineand a polyoxyalkylene glycol or a polyoxyalkylene glycol ether of anaromatic alcohol or of a polyhydric alcohol wherein the glycol or etherhas a molecular weight of between about 600 and about 4000 to 6000; forexample, dimethylamine and a polyoxyethylene glycol or a polyethyleneglycol ether of phenol or of :sorbitol having a molecular weight withinthe stated range. In the use of the combination, the monoamine is addedto an amount of from about 1.5% to 3.5% and the glycol or ether in anamount of from about 1% to 3%, both proportions being based upon theweight of the cellulose.

The spinning bath employed in coagulating the modified viscose may alsobe of conventional composition and may include from about 5% to 10%sulfuric acid, from about 1% to 15% zinc sulfate and from about 10% to25 sodium sulfate, preferably from 1% to 7% zinc sulfate and 15% to 22%sodium sulfate. Other metal sulfates, such as iron, manganese, nickeland the like may be present and may replace some of the zinc sulfate.The temperature of the spinning bath may vary from 25 C. to about C.,and is preferably between 45 C. and 70 C. to insure that the resultingregenerated cellulose filaments and fibers possess good physicalproperties, and especially tensile strength which suffers somewhat ascompared with conventional filaments, as will be more apparenthereafter.

From the spinning bath, and prior to washing, the filaments may bepassed through a stretch bath and stretched from about 25% to 145%during their passage through the bath. The stretch bath is maintained ata temperature between about C. and C. and may be a hot water bath or maycontain 1% to 5% sulfuric acid with or without from about 10% to 4% zincsulfate and from about 4% to 7% sodium sulfate.

The filaments are then subjected to the usual aftertreatments whichinclude washing and desulfurizing and, if desired, bleaching eitherbefore or after collection of the filaments. The filaments may or maynot be provided with a yarn finish before being dried.

The regenerated cellulose shaped products, such as filaments and fibers,formed in accordance with the present invention may be converted intofabrics using conventional processes and equipment. Preferably, suchfilaments and fibers are used alone but may be intimate ly blended with50 to 60% of conventional filaments or fibers without eliminating thebacteriostatic properties of the fabric.

The invention may be further illustrated by reference to the preparationof regenerated cellulose filaments from a viscose containing about 7.5%cellulose, about 6.5% caustic soda, and having a total carbon disulfidecontent of about 38.5%, based on the weight of the cellulose.

The viscose solution was prepared by xanthating alkali cellulose by theintroduction of 38.5% carbon disulfide based on the weight of thecellulose and churning for about 2 /2 hours. The cellulose xanthate wasthen dissolved in caustic soda solution. About 2.0% dimethylamine and1.3% of a polyoxyethylene glycol having a molecular weight of about 1500was added to and mixed with the viscose. Dry powdered commerciallyavailable 3,4,4'-trichlo.rocarbanilide was pasted by mixing with a smallamount of water to which Sterox AP had been added. After being wet out,water was added to give an 8.0% solid slurry with 0.05% Sterox AP, whichwas mixed for about 30 minutes at high speed.

The above-described dispersion of 3,4,4'-tri'chlorocarbanilide wasinjected into the viscose solution as it was extruded through aspinneret to form 600 denier, 400 filament yarns at a rate of about 50meters per minute. The coagulating and regenerating bath was maintainedat a temperature of about 60 C. and contained 10.0% sulfuric acid, 1.0%zinc sulfate and 21.0% sodium sulfate. The yarn was stretched about 50%while passing through a cascade bath (93 C.) of 5% acid. The yarn waspassed through the conventional rayon The cut sections of the samplepads were tested for bacteriostatic activity using the conventional pourplate method. In brief this method involves placing a test sample on anutrient agar which had been previously inoculated with a specificstrain of bacteria, with the Micrococczrs pyogenes, var. aureous strainof bacteria, being employed in the present instance. With the testsample in place on the inoculated agar plate the sample is incubated for24 hours at 37 C., after which the plate is examined. Bacteriostaticactivity is judged by the absence of bacterial growth around the testsample, as evidenced by the presence of a halo around the sampleperiphery. The halo size, that is, the width of the clear area, is takenas a measure of the degree of bacterial inhibition so that wide anddistinct halos denote excellent bacteriostatic properties. The areaunder the sample is also examined for signs of bacterial growth.Complete inhibition of growth under the same is termed No Growth in theContact Area (hereafter referred to as NGCA) and is considered to bepositive bacteriostatic activity, even in the absence of a halo.

The bacteriostatic properties of the various yarn samples noted abovewere as follows:

BACTERIOSTATIC ACTIVITY Sample Laundering Cycles (Percent3,4.4-trichlorocarbauilide based on weight Unlaundered 10 cycles 20cycles cycles of cellulose) 0.25 NGCA-irregular Numerous colonies haloof 1.5-2.0 of bacteria in conrnm. tact area. 0.50 NGCA-irregularNumerous colonies halo of 1.5-2.0 of bacteria in conmm. tact area. 1.0NGCA-halo of 1.0 Mostly no growth amp. plus a dim plus dim halo.

a 0. 2.0 NGOA1.0 mm. to NGOA2.1mm. NGCA-dim halo NGCA1.o-4.0ha1o.

5.0 mm. halo. Ealo plus dim 0.5 mm.

a o. 3.6 N GOA or around NGCA11.5 mm. N GOAhalo 2.0 NGCA-halo 2.7

contact area. halo. mm. to 5.0 mm. mm. to 3.5 mm.

processing cycle, including a hydrochlorite bleach bath, collected inspinning boxes, washed free of acids and salts and dried. Spinning ofthe modified viscose was completely satisfactory with no evidence offilter clogging or jet slubbing. The processed yarn contained 2.0% of3,4,4'-trichlorocarbanilide, based upon the weight of the cellulose, andwas white and soft.

Employing a viscose, spinning bath and procedure as described aboveadditional yarn samples were prepared, having 0.25%, 0.5%, 1.0%, and3.6% of 3,4,4'-trichlorocarbanilide, based upon the weight of thecellulose. Each of the yarn samples Was made into an individual pad bybeing first spread evenly over one-half of a cotton gauze fabric, afterwhich the uncovered half of the gauze was folded over the sample andthen stitched along the borders and across the pad width, bothperpendicularly and diagonally. During the laundering stage, shortsections were cut from the individual pads after the pads had beensubjected to selected number of laundering cycles, with the cut areas ofthe pads being stitched after each cutting thereof.

All samples were individually laundered in a Philco Bendix High CapacityAutomatic Washer, Model W 216, along with a 4-pound ballast fabric usinghot water (145 F.), A cup of All detergent, and warm rinse water. Aftera wash cycle of 9 minutes at high agitation speed, the wash load wassubjected to the usual rinse and spin cycle and oven dried at 75 C.

We claim:

1. A process for producing shaped bodies of regenerated cellulose whichhave bacteriost-atic properties which includes the steps of extrudingthrough a shaping orifice and into an aqueous acidic coagulatingsolution a viscose solution containing from about 4% to 10%, by weight,of cellulose having incorporated therein not less than 0.25%, by weightbased on said cellulose, of 3,4,4'-trichlorocarbanilide in particulateform to impart bacteriostatic properties to a dry-shaped product ofregenerated cellulose prepared from said solution, subjecting the thusextruded solution to the action of the aqueous acid solution until theextruded solution is coagulated, converting the coagulated solution toregenerated cellulose and subsequently drying the shaped products ofregenerated cellulose.

2. A process as defined in claim 1 wherein said viscose contains fromabout 1.0% to about 10% to 15%, by weight, based on said cellulose of3,4,4'-trichlorocarbanilide in particulate form.

3. A process as defined in claim 2 wherein said 3,4,4-trichlorocarbanilide is precipitated in the viscose from an organicsolvent solution.

4. A process as defined in claim 2 wherein said 3,4,4-trichlorocarbanilide is injected into the viscose in particulate formafter being precipitated in water containing a surface active agent froman organic solvent solution.

5. A process as defined in claim 2 wherein the 3,4,4'-

trichlorocarbanilide is injected into the viscose as a dispersionobtained by separation from an aqueous solution containing a surfaceactive agent and particles of attrited 3,4,4-trichlorocarbanilide havinga size of from about 2 to 7 microns.

6. A process as defined in claim 2 wherein the 3,4,4-trichlorocarbanilide is injected into the viscose as an aqueousdispersion containing a non-ionic surface active agent and3,4,4'-trichlorocarbanilide particles having an average size of fromabout 3 to 5 microns.

7 A process as defined in claim 6 wherein the injected particles of3,4,4'-trichlorocarbanilide having a size of not less than about 1micron.

8. A shaped product of regenerated cellulose having durablebacteriostatic properties formed by the process of claim 6.

References Cited by the Examiner UNITED STATES PATENTS 3,034,957 5/1962Smith et-al 16'738.5 3,161,622 12/1964 Harrington et al. 16738.6 XR

10 ALEXANDER H. BRODMERKEL, Primary Examiner.

L. HAYES, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,296,000 January 3, 1967 Gregory C. Bockno et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 4, line 56, for "10%" read 1% column 5,

11ne 48, for "hydrochlorite" read hypochlorite line 71, for "hot water"read hot wash water column 6,

line 18, for "same" read sample Signed and sealed this 26th day ofSeptember 1967.

( L) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner ofPatents

1. A PROCESS FOR PRODUCING SHAPED BODIES OF REGENERATED CELLULOSE WHICHHAVE BACTERIOSTATIC PROPERTIES WHICH INCLUDES THE STEPS OF EXTRUDINGTHROUGH A SHAPING ORIFICE AND INTO AN AQUEOUS ACIDIC COAGULATINGSOLUTION A VISCOSE SOLUTION CONTAINING FROM ABOUT 4% TO 10%, BY WEIGHT,OF CELLULOSE HAVING INCORPORATED THEREIN NOT LESS THAN 0.25%, BY WEIGHTBASED ON SAID CELLULOSE, OF 3,4,4''-TRICHLOROCARBANILIDE IN PARTICULATEFORM TO IMPART BACTERIOSTATIC PROPERTIES TO A DRY-SHAPED PRODUCT OFREGENERATED CELLULOSE PREPARED FROM SAID SOLUTION, SUBJECTING THE THUSEXTRUDED SOLUTION TO THE ACTION OF THE AQUEOUS ACID SOLUTION UNTIL THEEXTRUDED SOLUTION IS COAGULATED, CONVERTING THE COAGULATED SOLUTION TOREGENERATED CELLULOSE AND SUBSEQUENTLY DRYING THE SHAPED PRODUCTS OFREGENERATED CELLULOSE.